The goal of the proposed research is to use NMR spectroscopy and molecular biology tools to develop anti, HIV vaccines, inhibitors of HIV entry, and to obtain additional structural information about the Env protein, This will be pursued inthe greater context of the NCDDG grant in close collaboration with the laboratory of Dr. Reinherz. Our strategies will largely be based on our past research, in which we succeeded in converting poorly behaving proteins into molecules that are suitable for structural studies by NMR or crystallography. We will continue our efforts to engineer proteins to render them more soluble and stable, and to fold correctly when produced in established or novel expression systems. We will apply the expression and NMR technologies developed to define suitable C-terminal fragments ofHIV gp140 as anti-HIV vaccines, to develop fragments of Env suitable for high-throughput and NMR screening of compound libraries, and to obtain structural information on the V1V2 region of Env. The research will be pursued with four specific aims: 1. Develop procedures for production of soluble proteins suitable for vaccination, structural studies and library screemng. 2. Use NMR as a tool to design and validate soluble fragments of Env as potential HIV vaccines. 3. Develop general procedures for discovery of inhibitors of protein/protein interactions and search fbr small molecules that inhibit the gp120/CD4 interaction but do not trigger the conformational switch in Env that would enable interaction with chemokine receptors and trigger viral entry. 4. Define the structural properties of the V1V2 fragment and its role in shielding access of antibodies to the core of gp120.